Should a Truck Cap Hoist be this Difficult?

My F-350 came with a truck cap.  I wouldn't have gotten one for it, but it was already on there when I got it, it's color matched to the truck, and it has come in handy so I'm not going to complain.  However, I would like to be able to get it on and off without having to have a small army or helpers.  I did a search for hoists and there were surprisingly few out there so most guys have come up with their own but they look like they are way more involved than they should be.

I drew something up really quick but it's so simple that it makes me wonder if I'm missing something.  The gray box is the cap, the green lines 2x4's that would support the cap, yellow line is one continuous cable, and the orange circles are some sort of pulley.  The idea being that the cable would be secured to the ceiling at the upper left and run through a pulley at every corner.  If you heave on the end of the cable (arrow) would that lift the cap straight off the truck?  Seems too easy.

I tried to build something similar in my garage.  Basically it was a platform I could store the kiddos "outside" toys in the garage but out of the way. The original design was exactly what you have drawn up, but I couldn't get it to work.  When you pull on the cable, only the first corner lifts and the platform tilts up. It could have been due to the crappy pulleys I got from Home Depot, but I ended up scrapping that pulley system for a different one.  

Instead, I installed one of these at each end (two total):



Instead of the triangle hook, I used a chain attached at each end forming the triangle. Because it has 2 pulleys, it requires that there are 2 people lifting it together or you have to lift one end a couple feet, tie it off, lift the other end, tie it off, return to the first, etc.  Only real issue I've had with it is that you have to balance the weight from the left to right. 

Here's an old crappy cell phone pic of it:

Not sure of the weight difference (surely heavier). But I plan on just buying something similar to this for the hard top- the 4 door jeep hard top is heavy as **** to get off even with 2 people.. Price seems reasonable and they have a diagram I think at this link

http://m.outdoorplay.com/Harken-Jeep-Hoister?gclid=CL-Iwfvp0ssCFVE0aQodWqALOg

^^^ My neighbor has something similar for the topper on his Tacoma

If I tried doing it the way I had drawn it up, I figured on ordering some sailboat rigging to get it all done.  I thought about the sides raising unevenly, but wondered if using some good pulleys with ball bearings would help it run a little smoother.

That Harken looks similar to what a lot of guys do themselves...four separate lines going to one connection point and then a single line to hoist it up.  That just seemed like it was more complicated than it needed to be, but I suppose it's just a matter of getting all the lengths set up right the first time.

If you figure it out and its less than $100 bucks let me know. I also toyed with the idea of jerry rigging something but figured $140 wasn't bad.  I used to own a sailboat and the boating stores are extremely proud of their rigging gear!

Do you plan to leave yours suspended from the ceiling or just as an offloading mechanism?  I just want an easy way to take the top off.  Having the hard top is nice for winter and leaving stuff in the vehicle, but I have always owned soft top jeeps before and this hard top sucks when the weather is nice..

It would probably stay suspended for long periods at a time which is why it'd have to be on 2x4's so it doesn't warp over time.  I would have been fine spending a couple hundred bucks on something in order to avoid the hassle of getting all the individual pieces and making sure you put everything together right.

Why wouldn't you just attach the main pull line over one pulley and have the other end attached to a line that tugs on two ropes or points at either end?